Are Hydrangeas Poisonous?

Discover the dark secret lurking inside your beautiful hydrangea.



By: Julie A Martens

Botanical Names: bigleaf hydrangea (Hydrangea macrophylla), smooth hydrangea (Hydrangea arborescens) ‘Annabelle’, ‘Pee Gee’ hydrangea (Hydrangea paniculata)

Forget the panic you might feel at reading this story’s headline. Your prize hydrangea shrub in a pot on the patio, along with the stunning hydrangea garden design you carefully crafted, is not a huge health hazard. Is hydrangea poisonous? Technically, the answer is yes. Precisely, the answer is a little more involved.

Hydrangea plants, beloved for their showy flowers, have a darker side. Several parts of the plant — the buds, flowers and leaves — contain a compound known as glycoside amygdalin. It’s the amygdalin that has the potential to make hydrangea poisonous, because it can break down (in several different ways) to produce cyanide. The same substance is found in peach and plum pits and apple and pear seeds.

People and pets, including horses, dogs and cats, can experience hydrangea poisoning. For hydrangea poisoning to occur, a person or pet must eat very large quantities of the leaves, buds and/or flowers. There is one recorded case of a horse eating a potted hydrangea and becoming seriously poisoned. Typically hydrangea poisoning produces severe gastroenteritis symptoms, along with diarrhea, which is frequently bloody.

Interestingly enough, some individuals harvest hydrangea flowers to dry and smoke for a cheap high. According to pharmacists, dried hydrangea flowers produce effects similar to symptoms produced by tetrahydrocannabinol (THC), which is found in cannabis plants. In several European countries, a crime spree of hydrangea flowers from private and public gardens occurred during 2013 and 2014. The thieves’ intention was to dry the flowers, roll them with tobacco into cigarettes and smoke them for a cheaper-than-pot high.

The reason hydrangea flowers produce a euphoric feeling is because the amygdalin compound breaks down to produce cyanide-type effects in the cells in the body. Effectively, the cyanide deprives cells of oxygen. Most often hydrangea smokers report effects of dizziness, heart rate increases and euphoria, but if they smoke enough, the results can include intestinal and respiratory distress. It’s important to realize, though, that hydrogen cyanide is also present in cigarettes, so the potential to poison yourself with hydrangea, while present, is unlikely.

Is hydrangea poisonous? Technically yes, but most experts agree that the amount of the plant that would have to be consumed would be very large — and thus quite unlikely. Nonetheless, keep an eye on pets and small children around hydrangeas. Their smaller bodies would be more likely to suffer bad side effects from consuming this plant.

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